You don't need 11m+ sails to get the best out of an Ultrasonic something around 9.5-10 works equally as well if you get the right sail ie a slalom sail which are more powerful than a same size Formula sail. The ultrasonic is comfortable to be in the straps all day long whereas the Formula board is quite extreme but would plane marginally earlier. Lastly the Ultrasonic may plane through the lulls better than the 127 but having not tried them I couldn't say for definite.